Fig. 1. Construction site of PAL-XFEL.

Fig. 2. FEL undulator line plan of PAL-XFEL.

Fig. 3. ITF.

Fig. 4. Baseline gun for PAL-XFEL.

Fig. 5. A schematic diagram of the ITF beamline.

Fig. 6. Typical images of five screens (left to right: ‘Y1’ to ‘Y5’).

Fig. 7. Measured bunch charge versus laser injection phase for three different bunch charges.

Fig. 8. Electron energy and energy spread versus laser injection phase measured at the spectrometer D2.

Fig. 9. Three different transverse shapes of laser beam: Shape #1, #2 and #3.

Fig. 10. Emittance as a function of the gun solenoid current for three different shapes of laser beam.

Fig. 11. Emittance as a function of the gun solenoid current for three different laser injection phases using the laser beam transverse shape #2.

Fig. 12. Emittance as a function of the gun solenoid current for three different beam energies using the laser beam transverse shape #2.

Fig. 13. Emittance as a function of the gun solenoid current for three different bunch lengths in the case of an RF-gun energy of 5.5 MeV.

Fig. 14. Prototype HX undulator undergoing the pole tuning procedure.

Fig. 15. Measured effects of pole tuning at a 9.5 mm tuning gap. The residual fluctuation comes from the longitudinal positional error at the probe position, which is estimated to be about .

Fig. 16. Integration over a half-period around the th pole/peak position for the definition of the local- parameter.

Fig. 17. The measured local- changes due to a pole correction at the 9.5 mm tuning gap. The abscissa denotes the distance to the pole: 0 is the tuned pole itself, the two next-neighbor poles etc.

Fig. 18. Calculated pole gap correction based on the initial magnetic measurement and local- deviation. Most of poles need correction. The majority of those poles need a correction less than , some of them needed corrections. Except for the entrance and exit poles, which require larger correction, none are above this limit.

Fig. 19. Deviation of local for each pole before (black) and after pole tuning (red). The standard deviation before correction was , reduced to after correction.

Fig. 20. Measurement of gap reproducibility errors.

Fig. 21. Optical phase error at the working gap of 9.5 mm. The rms phase jitter is , which is within the specification of .

Fig. 22. Gap dependence of the optical phase error.

Table 1. Parameters of PAL-XFEL.

Table 2. Nominal operation parameters of ITF.

Table 3. Major parameters of the HXU undulator.